Re: SLR concerns, owners experiences please.

Bengt Cyren wrote:
Roger N. Clark wrote:

Noise varies by a large factor between cameras, largely due to the
size a each pixel in the sensor. What you are looking for, I think
is high ISO performance. High ISO performance is directly related to
pixel size, and in particular what is called the Unity Gain ISO
(which manufacturer's don't publish). The Unity Gain ISO varies by
about a factor of 16 from the smallest pixel size cameras to the
largest.

Yes, as I understand it, sensors has hardly developed regarding how
each area element collect photons and what the noise figure will be if
there are few photons. Therefore I want a large sensor with as few
pixels as possible (but no less than 4 MP). I'm probably different than
most consumers, as what I want hardly is what the camera manufacturers
are implementing.

Another factor to consider is that newer generation cameras
generally have better read noise, better fixed pattern noise,
better micro lenses, etc, all to maximize signal and
reduce noise. Thus a newer generation 8 megapixel camera
will likely give better images than an older generation
6 megapixel camera. But these improvements are only about
a factor of 2 or so, so the current crop of small cameras
with 8 to 10 megapixels is pushing pixel size too low in
my opinion.

I believe the limit for a useful picture is 1 MP. A noise free 2 MP cam
with a huge dynamic range, without halos and blooming, weighting in at
400 g would be terrific! (No, such a camera does not exist. As far as I
know, no camera have yet shown sufficient dynamic range.)

Well, such cameras do exist: check out some of the very light cameras
on the NASA Mars orbiters ;-) But they are pretty much out
of our price range ;-)

How much dynamic range do you want? Digital cameras have huge
dynamic range, but it is in the shadows, so learn to expose
digital correctly and it is not a problem. Just as you need
to expose slide film differently than print film, digital is
different from either.

A solution could be a small DSLR and a 50 mm f/1.8 lens.
The speed of the lens is a big boost in low light performance,
and 50 mm f/1.8 lenses are high performance and cheap (about $70).

Yes, but really, I want *one* piece of photographic gear and what it
should absolutely provide is wide-angle. I miss the 28 mm (eq) ability
of my Canon A50 so much, that this is the only requirement on my new
camera which can not be compromised. I know there are many super-zooms
out there, in particular from Panasonic, but most start at 35 mm (eq).
I never consider them, no matter what other benefits they may have.
Ricoh have interesting compacts, but these tend to deliver wide-angle
and nothing else. That's much too limiting, I think.

Depending on your subject, try mosaicking. Example:
http://www.clarkvision.com/photoinfo/large_mosaics

Since starting mosaics, I carry fewer wide angle lenses. With
mosaics, I choose the aspect ratio (e.g. square to long panorama),
and I end up with a higher resolution image. Some examples,
witch also include moving animals, and hand held:

http://www.clarkvision.com/galleries/gallery.africa/web/zebra.sunrise.c01.23.2007.JZ3F0891-6c-1200.html

http://www.clarkvision.com/galleries/gallery.africa/web/zebras.c01.23.2007.JZ3F0584-91d-800.html

http://www.clarkvision.com/galleries/gallery.africa/web/manyara.sunset.c01.17.2007.JZ3F7144-9b-800.html

http://www.clarkvision.com/galleries/gallery.africa/web/cheetah.c01.19.2007.JZ3F8148-9f-800.html

I agree. Quite frankly I think a lot of the technology in the SLR's
are outdated.

I disagree.

DSLRs are designed for speed and performance. Performance comes from
viewing through an optical viewfinder, which is the highest real time
you can get. If you have a LCD preview, when you want to take a
picture, the "live preview" mode must be turned off, the scene
metered, the focus set, ...

All this is done before hand when pressing the shutter halfway. Even
10 year old cameras does this pretty adequately, right?

...sensor chip cleared and prepared for the exposure, then the
exposure done.

Isn't this faster than physically moving a mirror? And doesn't moving a
mirror (which has mass) induce vibrations?

And the "live preview" is not real time, but delayed view as it takes
time to read the chip, which is great if you want delayed pictures to
miss the action!

Yea, but remember, when you compose using the screen, you can just turn
your eyes and look *directly* at the subject and press the shutter at
exactly the right moment. That is not possible when pressing your face
to an eyepiece. And if there is action, you can use your ears to decide
when to press.

Well, I guess all the pro wildlife and sports photographers
must be missing something, right? I think most would disagree
with this view, and so do I. Critical to action photography is
following the action while maintaining focus and composition.
See below.


Next, the time to prepare the chip and determine the exposure takes a
fair amount of time: people can turn away or the action is past peak
before the P&S camera takes the picture (this is called shutter lag).

I didn't know the time to "prepare the chip" was substantial. After
all, when capturing movies, even cheep compacts produce 30 exposures/s.

But the do that at reduced resolution (like 640x480 pixels), and
don't set the exposure for each frame. The can monitor the exposure
and adjust for the NEXT frame. And they don't do video in 1/30 second
from the live preview, but change modes which takes some time.

The DSLR has independent electronics to focus and another set of
electronics to measure and set exposure. The sensor chip sits behind
a shutter ready to take the picture, so all that has to be done is
raise the mirror and open the shutter. Even though this is a
mechanical step, it takes less time than all the other stuff a P&S
camera must do sequentially using the sensor.

My Fuji F10 has a shutter lag of 11 ms when prefocusing. Nikon D70s has
106 ms. (according to imaging-resource) An order of magnitude more!!
The SLR is faster when not pressing halfway. Is that important? Doesn't
you always do metering and set focus by half-pressing?

If wildlife and sports photographers did "half pressing" to get
the shot, they would miss the shot most of the time. So would the
parent trying to catch baby's first step, or their child's
great baseball catch.

A DSLR in action has two modes. "Quick draw" from when you press the
shutter button to when everything is "perfect." Example: this
rabbit bolted from the grass trying to escape from a serval cat
on the Serengeti. I quickly swung my lens over to it, composed
and pressed the shutter. The camera had to determine exposure,
lock on and take the shot.
http://www.clarkvision.com/galleries/gallery.africa/web/rabbit.c01.26.2007.JZ3F2215b-700.html

The mode most used in action photography does focus tracking:
the subject is moving toward or away from you, sometimes at rapid
speed (when the subject fills the frame it always seems rapid
because focus changes too fast to follow manually). The DSLR
autofocus system tracks the moving subject and computes the
rate of change of the focus, and when you press the shutter
button, the camera computes where the focus will be using
the rate of change and the known delay in raising the mirror.
Thus, the focus is predicted to be in the right spot at the
time when the shutter actually fires. Examples:

Grizzly bear fight:
http://www.clarkvision.com/galleries/gallery.bear/web/brown_bear.c09.09.2004.JZ3F4246.b-700.html

Birds in flight:
http://www.clarkvision.com/galleries/gallery.bird/web/eagle.c09.11.2004.JZ3F4717.b-700.html

http://www.clarkvision.com/galleries/gallery.bird/web/eagle.c01.18.2007.JZ3F7355b-700.html

Cheetahs:
http://www.clarkvision.com/galleries/gallery.africa/web/cheetah.c01.26.2007.JZ3F2429b-700.html

For the action images on my web pages, I generally use one
autofocus sensor, and I constantly change the active
sensor position depending on the composition I want for the
situation, keeping the sensor on the animal's eye(s).
I the animal changes directions (which is common), I shift
the sensor to the opposite position to keep the
composition the way I want it. The DSLRs I use have the
ability to quickly change sensor position with one hand
and in a fraction of a second.

In none of these situations could I have "half pressed" the
shutter and captured the action. This is also the case with
slower action: having a capable camera means more quality
images, whether a candid photo of a person at a party, or
the lion on the Serengeti on a zebra kill.

Roger

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